pymata-express

pymata-express

A high performance, Python asyncio client for the Arduino Firmata Protocol.

Pymata-Express is a Firmata client that, like its conventional Python sibling, pymata4, allows you to control an Arduino using the high-performance FirmataExpress sketch.

It supports both an enhanced version of StandardaFirmata 2.5.8, called FirmataExpress, as well as StandardFirmata and StandardFimataWiFi.

• FirmataExpress adds support for:
  • HC-SR04 Ultrasonic Distance Sensors using a single pin.
  • DHT Humidity/Temperature Sensors.
  • Stepper Motors.
  • Piezo Tone Generation.
  • Baud rate of 115200

Major features

• Fully documented intuitive API

• Python 3.7+ compatible.

• Set the pin mode and go!

• Data change events may be associated with a callback function or each pin can be polled for its last event change.

  • Each data change event is time stamped and logged.

• User's Guide, Including Examples.

• Implements 100% of the StandardFirmata Protocol (StandardFirmata 2.5.8).

• Advanced auto-detection of Arduino devices (when using FirmataExpress).

Here is an example that monitors for data changes on a digital input pin.

import asyncio
import time
import sys
from pymata_express import pymata_express

"""
Setup a pin for digital input and monitor its changes
using a callback.
"""

# Setup a pin for analog input and monitor its changes
DIGITAL_PIN = 12  # arduino pin number
IDLE_TIME = .001  # number of seconds for idle loop to sleep

# Callback data indices
# Callback data indices
CB_PIN_MODE = 0
CB_PIN = 1
CB_VALUE = 2
CB_TIME = 3


async def the_callback(data):
    """
    A callback function to report data changes.
    This will print the pin number, its reported value and
    the date and time when the change occurred

    :param data: [pin, current reported value, pin_mode, timestamp]
    """
    date = time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(data[CB_TIME]))
    print(f'Pin: {data[CB_PIN]} Value: {data[CB_VALUE]} Time Stamp: {date}')


async def digital_in(my_board, pin):
    """
     This function establishes the pin as a
     digital input. Any changes on this pin will
     be reported through the call back function.

     :param my_board: a pymata_express instance
     :param pin: Arduino pin number
     """

    # set the pin mode
    await my_board.set_pin_mode_digital_input(pin, callback=the_callback)

    while True:
        try:
            await asyncio.sleep(IDLE_TIME)
        except KeyboardInterrupt:
            await board.shutdown()
            sys.exit(0)

# get the event loop
loop = asyncio.get_event_loop()

# instantiate pymata_express
board = pymata_express.PymataExpress()

try:
    # start the main function
    loop.run_until_complete(digital_in(board, 12))
except (KeyboardInterrupt, RuntimeError) as e:
    loop.run_until_complete(board.shutdown())
    sys.exit(0)

Sample console output as input change events occur:

Pin: 12 Value: 0 Time Stamp: 2020-03-10 13:26:22
Pin: 12 Value: 1 Time Stamp: 2020-03-10 13:26:27